1. Field of the Invention
The invention relates to a hollow valve plate for liquid-cooled valves of a piston compressor having a half shell with cooling channels that are open on one side and that are covered up by a thin reed plate, which is sealed at least along the cooling channels, and includes elements of the valves that are machined from said plate and connected in one piece on one side.
2. The Prior Art
Especially when used as a brake air compressor in motor vehicles or the like running frequently for long periods of time at high power, it is necessary to actively cool the valve plate carrying at least one suction valve and one pressure valve to prevent overheating in this area and to pre-cool, at least to a certain degree, the compressed air that is expelled via the pressure valves, before the air is then, in most cases, further cooled inside the cylinder head area prior to being discharged. According to the prior art, for this purpose, valve plates are used that are hollow in some areas and/or provided with cooling channels, and the cooling chambers and/or cooling channels of which are connected to a liquid cooling system of the piston compressor, and/or connected together with the same to the liquid cooling of an internal combustion engine used for powering a motor vehicle.
The current prior art for producing such hollow valve plates usually envisions brazing. The individual parts to be brazed therein are a number of thin-stamped steel plates which are connected in packets so as to form one unit, wherein from meander-shaped cutouts and recesses in some areas of the middle plates together with the outer plates, which are closed except for inflow and outflow openings, cooling channels or cooling chambers are created. However, there are also embodiments having two half-shells (mostly made of grey cast iron), which comprise channels or areas that are open on one side and which, when being assembled, form closed three-dimensional channels and/or chambers on the inside. Both embodied variants provide, in most cases, that suction fins or pressure fins are finally fastened via a receptacle or the like on the valve plate.
Aside from the fact that the known valve plates therefore comprise a relatively high number of individual parts and are also quite complicated in terms of production and assembly, they also suffer from the disadvantage that the clearance created on the cylinder side, meaning the design-related dead space that cannot be compressed any further, is quite large, which has a negative influence on the volumetric efficiency of the compressor.
Furthermore, W02011/124502A1 discloses a hollow valve plate of the type as described in the introduction that provides for a reed plate, which is, for example, known from DE1628187A1 or EP 846227A1, that covers the totality of the valve plate and is clamped to the same between cylinder and cylinder head, and that serves, simultaneously, for closing, on the cylinder side, the cooling channels, which are open on the cylinder side. By omitting the separate second half-shell and/or reed plate on the cylinder side, which formed and/or closed until now these channels on the cooled valve plates, not only was it possible to achieve a considerable simplification in terms of production and assembly of such hollow valve plates, but also a substantial reduction of the clearance on the cylinder side. In addition, sealing of the total system was simplified, because one sealing level is omitted. The associated savings resulting from less weight and reduced costs were also advantageous.
Therefore, it is the object of the present invention to improve a hollow valve plate of the kind as described in the introduction in such a manner that the achieved advantages can be maintained unchanged also independently of the concrete configuration of the suction side of the valve plate, and thereby for a larger number of different configurations of piston compressors.